doris/array_first.md at ebc8988f70978d052d26a47e696c4ce9be9916c9

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amory 1f032a551d [Improve](array-functions) support array first function (#20397 )

add array_first(lambda, [1,2,3,null]) function for doris

2023-06-06 12:08:46 +08:00

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title, language

title	language
array_first	zh-CN

array_first

description

返回数组中的第一个func(arr1[i])值不为0的元素。当数组中所有元素进行func(arr1[i])都为0时，结果返回NULL值。

Syntax

T array_first(lambda, ARRAY<T>)

使用一个lambda表达式和一个ARRAY作为输入参数，lambda表达式为布尔型，用于对ARRAY中的每个元素进行判断返回值。

notice

仅支持向量化引擎中使用

example

mysql> select array_first(x->x>2, [1,2,3,0]) ;
+------------------------------------------------------------------------------------------------+
| array_first(array_filter(ARRAY(1, 2, 3, 0), array_map([x] -> x(0) > 2, ARRAY(1, 2, 3, 0))), -1) |
+------------------------------------------------------------------------------------------------+
|                                                                                              3 |
+------------------------------------------------------------------------------------------------+


mysql> select array_first(x->x>4, [1,2,3,0]) ; 
+------------------------------------------------------------------------------------------------+
| array_first(array_filter(ARRAY(1, 2, 3, 0), array_map([x] -> x(0) > 4, ARRAY(1, 2, 3, 0))), -1) |
+------------------------------------------------------------------------------------------------+
|                                                                                           NULL |
+------------------------------------------------------------------------------------------------+


mysql> select array_first(x->x>1, [1,2,3,0]) ;
+---------------------------------------------------------------------------------------------+
| array_first(array_filter(ARRAY(1, 2, 3, 0), array_map([x] -> x > 1, ARRAY(1, 2, 3, 0))), 1) |
+---------------------------------------------------------------------------------------------+
|                                                                                           2 |
+---------------------------------------------------------------------------------------------+

keywords

ARRAY, LAST, array_first

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